Tube mills are employed in particular to mill-dry coal (VGB Kraftwerkstechnik 67 [1987], 12, 1185-92). Air is pumped through the tube inside into the milling area while raw coal is supplied, and the milled coal is removed while suspended in air through the annular space around the tube. The raw coal is supplied to the milling area with a feed screw that rotates along with the tube. The screw's threads are loosely attached to the tube by chains. The tube and screw are connected to a shaft mounted in a loose bearing outside the mill. The bearing must be able to accommodate axial displacements of the shaft, thrusts, and impacts, and eccentricities on the part of the loosely suspended screw.